Obama Meets Raul Castro at Mandela Memorial

They shook hands. For a former subcontractor stuck in Cuba, that could mean a lot.

President Obama shakes hands with Cuban President Raul Castro during the memorial service for former South African President Nelson Mandela at FNB Stadium, Dec. 10, 2013, in Johannesburg.(Chip Somodevilla/Getty Images)

President Obama met Cuban President Raul Castro for a handshake at Tuesday's memorial for Nelson Mandela in South Africa. While Obama isn't the first U.S. official to meet with Castro, the meeting comes at a particularly interesting time in Cuba-U.S. relations.

Four years ago, former U.S. subcontractor Alan Gross was arrested in Cuba and eventually convicted of "acts against the independence or territorial integrity of the state." He was sentenced to 15 years in jail. Earlier this month, on the four-year anniversary of his arrest, Gross wrote an open letter to the president. "I have lost almost everything in the last four years," he wrote. He continued:

With the utmost respect, Mr. President, I fear that my government – the very government I was serving when I began this nightmare – has abandoned me. Officials in your administration have expressed sympathy and called for my unconditional release, and I very much appreciate that. But it has not brought me home.

It is clear to me, Mr. President, that only with your personal involvement can my release be secured.

A handshake alone doesn't constitute action. But a warming of relations with Castro, who asked to meet with Obama soon after Obama won his first election in 2008, could be a major step in the direction that Gross is specifically asking for.